1. Field of the Invention
This invention relates to a supporting element for instruments or speakers, and in particular relates to improvement of a supporting element for the purpose of giving such instruments as piano, organ, harpsichord, marimba, drum set, koto, harmonica with keyboard, and guitar, or speakers freedom to vibrate along the vertical and horizontal directions.
2. Description of Related Art
In order to reduce, as much as possible, the distortion of the sound vibrations generated from such instruments as piano, organ, harpsichord, marimba, drum set, koto, harmonica with keyboard, and guitar, or speakers, and at the same time, to create a good acoustic space, the supporting conditions which do not prevent the freedom of vibrations when being played or used should be secured.
As an example, the supporting conditions will be described for a grand piano (1) for concert hall illustrated in FIG. 13. Mounted onto the bottom end of the leg (2) are a caster (3) that makes it easy for the piano to move in the hall and a braking means (4) for positioning and fixing thereof. Between the center O1 of the wheel (3A) of the caster (3) and the axial center O2 of the leg (2), a certain eccentric distance e is set to facilitate changing the direction of rotation of the wheel (3A).
As a result, the vertical component force F1 that corresponds to the weight of the piano (1) and the horizontal component force F2 that is parallel to the floor (F.L) are exerted on the leg (2). When the horizontal component force F2 is exerted on the leg (2), a bending moment M is produced on the main body of the piano, particularly, on the leg (2), owing to the existence of the eccentric distance e.
When the bending moment is applied on the leg (2), the grand piano (1), when being played, is prevented from freely vibrating in the vertical and horizontal directions. As a result, distortions are to be generated in the waveforms of the sound vibration produced from the main body of the grand piano (1). When the waveforms of the sound vibration are distorted, the direction of sound waves and the maintenance of sound quality should, naturally, be affected badly, and expected effects of performance cannot be obtained in spite of the greatest efforts of a performer and a tuning specialist.
On the other hand, the speaker (6) illustrated in FIG. 14 is generally placed and used on the floor (F.L) or on a frame stand, which is not shown. Then, the bottom surface (7) of the speaker (6) comes in close contact, in a plane touch, with the floor (F.L) or with the top surface of the frame stand. Therefore, since the free vibration both in the vertical and horizontal directions is restricted, the sound waves produced by the main body of the speaker (6) are distorted and transmitted to the air as they are. As a result, differences in the direction, the amplitude, or the time period of sound waves are produced between the sound vibrations directly transmitted from the speaker (6) to the air and those sound vibrations transmitted by way of the floor (F.L) or the frame stand to the air. Hence, close reproduction of the sound quality becomes impossible.
In order to solve the above-mentioned problem, there are some methods attempted in the case of the grand piano (1) illustrated in FIG. 13. Among them are the followings: as a positioning and fixing element for the piano main body, a frame stand of saucer type (the figure omitted) made of synthetic rubber or wood is placed between the wheel (3A) of a caster (3) and the floor (F.L); secondly, the moving direction of the wheel (3A) along the floor (F.L), that is, the acting direction of the horizontal component force F2 produced by the weight W, is made either parallel or perpendicular to the longitudinal direction of the sounding board or rod (the figures of both omitted) that is installed in the piano main body.
In any case of the above-mentioned weight supporting systems, however, the fact that there is an eccentric distance e between the center O1 of the wheel shaft (3B) of a caster (3) and the center O2 of the leg remains unchanged. Therefore, it is impossible to eliminate the influence of the bending moment M that is produced by the horizontal component force F2 completely.
It follows that there is a considerable phase difference between the sound waves transmitted from the main body of the grand piano (1) through the air to the space and those sound waves transmitted through the leg (2), the caster (3), and the floor (F.L) to the space. Especially on the side of the leg (2), the sound waves are transmitted to the floor (F.L) by way of the leg (2) and the wheel (3A) of the caster (3) adversely affected by the bending moment M. Accordingly the disturbance of waveforms of sound vibration becomes more remarkable. Thus, in spite of the various countermeasures mentioned above, the direction of sound transmission and the improvement of sound quality are prohibited to a great extent.
Then, the wheel (3A) of a caster (3) comes in close contact with the floor (F.L) over a comparatively narrow area. As a result, the weight W exerted on a unit area of the floor (F.L) becomes large, the vibrations are more easily transmitted to the floor (F.L), and the waveforms of sound vibration are disturbed all the more. Furthermore, since a large weight W is exerted on the floor (F.L) by way of a caster (3), the floor (F.L) may be damaged or hollowed.
On the other hand, in the case of the speaker (6) illustrated in FIG. 14, the disturbance of waveforms of sound vibration caused by the horizontal component force F2 and the bending moment M, as seen with the above-mentioned grand piano, is not the major problem, because there is no caster between the bottom end of the speaker (6) and the floor (F.L). However, since the whole area of the bottom end (7) of the speaker (6) closely touches the floor (F.L), the weight W of the speaker (6) is spread over and conveyed to the floor (F.L) as divided weights. As a result, the free vibrations of the speaker (6) in the vertical and horizontal directions are restrained as in the case of grand piano (1), and a resounding phenomenon of the floor takes place.
To solve this problem in a conventional manner, a supporting material such as brick, concrete block, and wood material is placed between the bottom end surface (7) of the speaker (6) and the floor (F.L) or the frame stand supporting the speaker (6), trying to restrain the transmission of vibrations to the floor and thereby to reduce the disturbance of waveforms of sound vibration. Such a weight supporting system, however, did not give sufficient damping effects and the risk of secondary troubles such as floor resounding to take place was not completely removed.
To solve such a problem, a speaker-supporting element illustrated in FIG. 15 is on sale. This speaker-supporting element forms a one-point support system, wherein a columnar pedestal (21) having a flat ball-receiving surface (22A) is placed on the floor (F.L), then, under this condition, a steel ball (20) is put on the ball-receiving surface (22A), and furthermore, a columnar pedestal (21) having a semi-spherical ball-receiving surface is covered on the steel ball. Between the ball-receiving surfaces (21A) (22A) vertically placed face to face turns and moves the steel ball (20), and thereby the vibrations in the horizontal direction are damped to a considerable extent. However, this speaker-supporting element can hardly give an effect in damping the vibrations in the vertical direction transmitted from the speaker (6), because the pedestals (21) (22) and the steel ball (20) are made of rigid material and the vertical movement of the steel ball (20) is substantially prohibited due to its construction. Besides, on the flat ball-receiving surface (22A) turns and moves the steel ball (20) freely along the horizontal direction, and thus, a difference of position between upper and lower pedestals (21) (22) is liable to arise while the supporting element is attached to the bottom surface of the speaker (6). As a result, the stable positioning and supporting of the speaker (6) are prevented.
Taking these present circumstances into account, the inventor repeated a series of systematic experiments to investigate the characteristics of the vibrations transmitted from an instrument or a speaker to a supporting element. The supporting element thus invented from the results is presented as Japanese Patent No. 2593404. The use of this type of supporting element can actually reduce the differences in direction, amplitude, or period of sound waves between the vibrations directly transmitted from an instrument or a speaker to the air and those vibrations transmitted by way of the floor or the frame stand to the air. Though, the inventor also continued thereafter to do additional experiments on the damping characteristics that a supporting element for instruments or speakers should have. As a result, the inventor has found the following fact: the quality of sounds produced by an instrument or a speaker can be reproduced almost perfectly, if the main part of the supporting element is made with spring materials and, at the same time, the weight-supporting part in a point touch or line touch and the vibration-absorbing part, both of which make use of spring elasticity, are placed together between the instrument or the speaker and the base plate or the floor.